does anyone knows the specifications for the InDesign XPath subset? very often my XPath definitions work like a charme in Oxygen XML Editor but InDesign is ignoring them when importing XML files for mapping styles.

When you choose to run an XPath in Oxygen you can set the XPath type to XPath 1.0.But I really do not know anything about the XPath 1.0 subset implemented in InDesign. Maybe you could find an InDesign users list and ask there.